Emissions Analysis for a Transit Corridor Under Different Improvement Strategies

This paper attempts to quantify the emission reduction from different improvement strategies in a transit corridor. Two strategies—the use of transit signal priority (TSP) and the enhancement of bus lane utilization—were considered. Chaoyang Road, a 17-km arterial road in Beijing, China, was chosen as the study corridor. A microsimulation model was developed in Vissim. GPS-instrumented vehicle data from 30 passenger cars and 15 buses were used to calibrate the model. Passive and active TSP strategies and different schemes of bus lane utilization, corresponding to five scenarios, were designed. The microsimulation model was used with vehicle-specific power calculations to estimate emissions for various scenarios. The results showed that the corridor benefited from TSP, with the reduction of nitrogen oxides (NO_x) and hydrocarbon (HC) emissions. Moreover, the enhancement of bus lane utilization has positive or negative effects on emissions in the corridor depending on whether the utilization rate reaches a suitable value. The scheme of bus lane utilization in which three regular routes were permitted to use the bus lane outperformed the other three schemes. In this scheme, all emissions were reduced over a base case [carbon dioxide (CO₂) reductions of 4%]. Increased bus service on the bus lane that was not optimized still reduced NO_x and HC emissions relative to the base case but increased CO₂ emissions by as much as 2%. The findings can be used to develop operational strategies that focus on both environment benefits and delay reductions for a transit corridor.